1. Field of the Invention
The present invention relates to a driving assistance apparatus.
2. Description of the Related Art
Conventionally, there is reported a technique that monitors a moving body existing laterally ahead of a vehicle in an intersection or similar place using a peripheral detection sensor such as a radar (for example, in Japanese Patent Application Laid-open No. 2008-152389 and Japanese Patent Application Laid-open No. 2011-253241). This conventional technique changes the preliminarily set detection range of the peripheral detection sensor as necessary corresponding to the distance between the moving body to be the assistance target of driving assistance and own vehicle on which the peripheral detection sensor is mounted, and monitors the moving body of the assistance target within the changed detection range.
Now, in the conventional technique (for example, in Japanese Patent Application Laid-open No. 2008-152389 and Japanese Patent Application Laid-open No. 2011-253241), in the case where the moving body of the assistance target moves in a direction different from the initially assumed direction even when the detection range is changed corresponding to the distance between the moving body as the assistance target and the own vehicle, the assistance target to be monitored might become out of the changed detection range in the course of movement.
Here, in driving assistance in an intersection, the direction in which the assistance target to be monitored approaches the own vehicle can be roughly assumed based on traffic accident statistics in the past and Road Structure Ordinance. However, in practice, there are a lot of unexpected road structures and movements of the moving body.
For example, as illustrated in FIG. 1, assume that the situation where a moving body to be the assistance target of driving assistance (in FIG. 1, the other person's vehicle approaching the own vehicle from the right side of the own vehicle) is monitored using a peripheral detection sensor. The peripheral detection sensor allows detection within the detection range set to include a predetermined region laterally ahead of the own vehicle (in FIG. 1, the ribbon-shaped region that is centered on the front side of the own vehicle and expands in the right-left direction). In the situation illustrated in FIG. 1, the moving body existing in the position out of the detection range of the peripheral detection sensor (in FIG. 1, out of the ribbon-shaped region) can be removed from the assistance target of the driving assistance so as to reduce the unnecessary driving assistance.
However, for example, as illustrated in FIG. 2, in the case where a moving body (in FIG. 2, the pedestrian crossing at the crosswalk that continues from the right side obliquely to the left side of the own vehicle) moves not along a predetermined region (in FIG. 2, a ribbon-shaped region) that is set assuming the installation angle of the road in the intersection, the moving body might become out of the detection range of the peripheral detection sensor as a result of movement of the moving body as the assistance target to be monitored. In addition to this situation illustrated in FIG. 2, also in the situation of the encounter with an intersection having an exceptional road intersecting angle or in the situation where the own vehicle approaches an intersection at a certain angle, the assistance target to be monitored might become out of the detection range.
Therefore, it is possible to extend the sensor range so as to reliably monitor the assistance target to be monitored. However, the moving body other than the assistance target to be monitored might be unnecessarily detected. Accordingly, it is not preferred to extend the detection range of the peripheral detection sensor without careful consideration.
There is a need for a driving assistance apparatus that allows suitably changing a detection range of a peripheral detection sensor to include the future movement point of a moving body of an assistance target without unnecessarily detecting a moving body other than the assistance target.